Gymnastic exercisers commonly utilized in homes or exercising rooms, including stationary bicycles and climbing exercisers, etc., have energy absorbing devices therein, which are adapted to be driven by an exercising person via power transmission systems, for converting the mechanical energy generated by the exercising person into heat. Therefore, the exercising person can exercise in a small place, yet still get enough exercising effect. This kind of gymnastic exercisers is compact and convenient, and, different exercising effects can be achieved by different power transmission system.
There are different types of energy absorbing devices, which include: 1) the friction type, which usually has a flywheel with a friction belt wraped thereon. The friction force can be adjusted. Some examples of this type are disclosed in U.S. Pat. No. 3995491 to Wolfla, II, and U.S. Pat. No. 4533136 to Smith et al. 2) the vaned type, disclosed in U.S. Pat. No. 4188030 to Hooper, which drives a large vaned wheel via gears and sprockets, to absorb energy by movement of the broad surfaces of the vanes against the surrounding body of air. The friction force can not be adjusted.
The two types of energy absorbing devices as listed above have deficiencies respectively. The friction force of the friction type is a constant value, and the static friction force is larger than the dynamic friction force. As a result, the exercising person feels its hard to start, but the friction force can not be increased when the rotating speed is high, thus diminishing the exercising effect. If the friction force is raised to increase the exercising effect, the wheel can hardly be started by the exercising person. Furthermore, the exercising effect of this type is not satisfactory. Besides, when the friction belt is worn out, the user can rarely find a replacement, which make the entire exerciser useless. Other shortcomings include: the exerciser is difficult to move due to the heavy flywheel, and the high frequency noises emitted because of friction between the friction belt and the flywheel are difficult to bear.
The friction force of the vaned type increases along with the rotating speed of the vanes. Therefore, the exercising effect is greater than that of the friction type. The vaned type does not have the shortcomings of being hard to start and of the friction belt wearing. But, the vaned wheel will generate unbearable noises. In addition, the side effects of the cold wind create problems for the exercising user when the device is used in cold regions or during cold seasons. Other disadvantages of the vaned type include its tremendous size, and the unadjustable resisting force.